In Reply to: One More Consideration posted by Jim Conforti on April 30, 2000 at 20:21:25:
There is a certain harmonic balance needed by the engine. BOth the pulley and the flywheel provide the balance. If you replace one , that is fine, if you replace both you are going to do just as Jim C. says.
I saw a 95 M3 that had both, and the rear drive train was literally wrenched from underneath the car, and the engine was loused to the highest order.
I have an underdrive pulley, and so far it is great. I've heard good things about flywheels as well.
I have heard that flywheels are better for auto-x and track events, b/c they allow the engine to rev faster and perform negative acceleration duties.
the UD pulley will give you more torque through the powerband, it will make your car have a heftier bottom end to match the better high end that a chip, intake, or even exhaust can give you.